1. Field of the Invention
The present invention relates to a surface treatment for improving the seizure resistance of a mechanical element or component having a sliding surface (referred to hereinafter as a xe2x80x9csliding memberxe2x80x9d) such as gears, bearings, etc., and in further detail, it relates to a sliding member having excellent seizure resistance having a sulfide-based solid lubricant layer on the sliding surface of a metallic member.
2. Description of the Related Art
Mechanical components such as various types of gears, bearings, pins or pivots, pistons or cylinders, etc., which move in contact with the surface of the metallic counter member, suffer problems of abnormal wear and seizure even in the presence of a lubricant oil. As a means of reducing such problems, it is known to form a solid lubricant layer based on sulfides such as an iron sulfide, a molybdenum sulfide, or a tungsten sulfide, etc., on the surface of the sliding member (particularly, a steel member).
As a means for forming a sulfide-based solid lubricant layer on the surface of a metallic member, generally known method is employing an electrochemical process. A representative method comprises performing electrolysis in an alkaline electrolytic solution by using the metallic member as the anode, thereby depositing a sulfide on the surface of the metallic member used as the anode. In addition to the anodic sulfurization treatment above, there is also known a special method comprising performing a treatment in a fused salt bath by using the metallic member as the cathode.
For instance, if an iron-based article is subjected to electrolytic treatment in a fused salt of potassium thiocyanate and sodium thiocyanate, the Fe component originating from the iron-based component and the S component from the bath react to form a sulfurized layer (an FeS based component) on the surface of the component. The sulfurization treatment technology is disclosed in Japanese Patent Publication JP-B 1809/1969, Japanese Patent Publication JP-B 12158/1988, and Japanese Patent JP-A 220689/1994. The patent publications above teach using a fused salt bath containing potassium thiocyanate and sodium thiocyanate mixed at a ratio of about 3 to 1, and preferably performing the electrolysis at a temperature of about 190xc2x15xc2x0 C. and at a current density in a range of from 1.5 to 4.0 A/dm2.
A sliding member having a sulfide-based solid lubricating layer on the sliding plane thereof generally exhibits an excellent seizure resistance; however, to improve the life of machines, it is pertinently required to further increase the seizure resistance.
Accordingly, an object of the present invention is to fulfill this requirement. The present invention provides a novel and a simple production method capable of realizing a sliding member which achieves the requirement above in a industrially advantageous manner.